1. Field of the Invention
The present invention relates to a device for the galvanic precipitation of aluminum from aprotic, oxygen- and water-free, aluminum organic electrolytes. More particularly, the invention relates to such a device having a galvanizing tub, sealed from the outside and charged with a protective atmosphere, having an annularly closed galvanizing trough comprising a contacting and holding means within the tub, rotatable around a vertical axis of rotation and with support arms for good holders proceeding in a horizontal plane; and comprising separate charging and discharging passageways attached to the galvanizing tub, each consisting of a preliminary and a main chamber and having goods transfer devices, which are serviceable from the outside, disposed therein.
2. Description of the Prior Art
A galvanic precipitation device of this type has been disclosed by German Letters Patent No. 2,716,805. In this known device, the charging and discharging passageways are located above the galvanizing tub, and are subdivided into a preliminary and main chamber which are connected to one another by a sliding door. When the sliding door is opened, a hydraulically or pneumatically actuable workpiece transfer device provides for the introduction of the goods carriers or holders. With the annular design of the electrolyte trough, the goods carriers can move in a circular path through the electrolyte with the contacting and holding means and, given high current densities, can be coated with aluminum. Additionally, the annular design of the electrolyte trough makes possible the spatial separation of the feeding and removing of the goods carriers, using the charging and discharging passageways.
The contacting and holding device preferably exhibits a plurality of support arms, with the charging and discharging passageways matched to the divisional spacing of the carrying arms. Also, the various carrying arms can be separately supplied with an electrical current, so that different precipitation conditions can be selectively set for various work pieces. When so spatially arranged, the individual carrying arms can be loaded and/or unloaded simultaneously in a clock-like or pulsed manner without any great interruptions.
In this known device, the main chamber is designed as a condensation space and it is equipped with a spray device for spraying a solvent which is compatible with the electrolyte. The finished, galvanized goods can be freed of any adhering electrolyte residues in the primary chamber of the discharge passageway using this spray device.
In a preferred embodiment of the known device, a container for a pre-treatment bath is disposed in the preliminary chamber of the charging passageway (or lock), and a container for a post-treatment bath is located in the preliminary chamber of the discharging passageway (or lock). By so doing, the pre- and post-treatment of the work pieces may also be incorporated in the lock area of the galvanizing device which has been charged with a protective atmosphere. Thus, the economic feasibility, quality, and safety of the galvanic aluminization is further increased.
The disadvantages of this known galvanizing device include not only the complicated structure of the system, particularly of the work piece transfer device, which is a great hindrance to commercial exploitation on a large scale, but also the design of the passageway or lock is ineffective for keeping air and humidity away from the electrolyte, thus causing the slow deterioration of the electrolyte.
An aluminization cell has been disclosed in German OS No. 2,901,586, in which a lock system utilizing a fluid lock for the introduction and removal of the goods which are to be galvanized is provided. A preliminary chamber exhibiting a feed opening and which can be flooded with an inert gas precedes the fluid lock. The diffusion of oxygen and atmospheric humidity into the system can be prevented to a large extent with such a lock system. Using a continuous conveyor belt, the goods to be galvanized are introduced on goods frames or holders from the preliminary chamber which has been flooded with an inert gas into the galvanizing trough through the fluid lock. After galvanization they can be ejected from the trough with the assistance of the same conveyor belt in the reverse direction. The disadvantageous aspect of this known device is that a considerable amount of the electrolyte is carried out of the electrolyte trough and into the fluid lock. Due to this continuing contamination of the lock fluid with the electrolyte and thereafter the unavoidable reaction with traces of air and humidity in the preliminary chamber, flooded with inert gas, the reaction products precipitate at unfavorable locations on the goods which have been previously cleaned and are to be aluminum-coated. These are conveyed into the galvanizing space through the fluid which simultaneously functions as an entry and exit lock. These parts can no longer be coated with a technically usable aluminum coating. Additionally, such a cell for the aluminum galvanization of mass-produced goods is not economical, since only one goods holder--which cannot be uncoupled from the conveyor belt during the galvinization, can be coated.